Fig. 4.

Age-specific proportion of the population immune to symptomatic SARS-CoV-2 infection from February 17, 2021 to August 1, 2022. (A–F) The lines show the time-dependent proportion of people immune to symptomatic SARS-CoV-2 infection among those aged from 20 to 29 (A), 30–39 (B), 40–49 (C), 50–59 (D), 60–69 (E), and ≥ 70 (F) years, and the shaded areas are their 95% confidence intervals (CIs), computed via the bootstrapping method. The red lines reflect the scenarios in which the immunity from natural infection as well as the immunity from the second and third vaccine doses are considered, whereas the light blue lines reflect the scenarios in which only the immunity from the second and third vaccine doses is taken into account. The projection was performed on April 10, 2022, and the estimates afterward are from a model-based projection.